1. Field of the Invention
This invention relates to a sheet transport system and apparatus for an image-forming apparatus, and particularly to a sheet transport system and apparatus for an image-forming apparatus including a scanner unit arranged on an upper part of an image-forming unit.
2. Description of the Background Art
An image-forming apparatus may include a straight feeding sheet path system and a turn-around feeding sheet path system.
The straight feeding sheet path system ejects a sheet with an image formed thereon substantially horizontally from an image-forming unit to an ejected sheet stacker from a sheet chute. The straight feeding sheet path system has an advantage that when thick or hard paper sheets, such as postcards, are used as printing papers, these printing papers are not bent and do not curve in the straight feeding sheet path system.
On the other hand, the turn-around feeding sheet path system ejects printing papers from an image-forming unit to an ejected sheet stacker in a different direction of the sheet chute than in the straight feeding sheet path system. An image-forming apparatus employing such a turn-around feeding sheet path system can be smaller in size in comparison with an image-forming apparatus employing the straight feeding sheet path system.
An image-forming apparatus with a turn-around feeding sheet path system may eject printing papers from an ejected sheet stacker into a sheet stacker which is in an inner area of an upper projection of an apparatus main body. Therefore, in the image-forming apparatus with a turn-around feeding sheet path system, the body size of the apparatus is not influenced by the size of the printing sheets. Furthermore, image-formed sheets (i.e. sheets which have images formed thereon) of the image-forming apparatus with the turn-around feeding sheet path system are automatically sorted on output from the ejected sheet stacker. Therefore, a user does not need to rearrange the image-formed paper sheets after they are output.
Also, an image-forming apparatus can utilize a combined system of the above two feeding sheet path systems. A combined system may have some of the advantages of both of the above two systems. One type of system attempts to select either the straight feeding sheet path system or the turn-around sheet path system by utilizing a path selector. For example, U.S. Pat. No. 4,750,016 discloses an image forming apparatus which utilizes a path selector which selects feeding sheet paths by adjusting an axis of the path selector by a movement of a pivotally supported tray.
Recently, processor units, for example personal computers, have been designed to have printer controls. Printers themselves utilized with these personal computers may not include a manual operation panel, because a clear appearance of the printer may be preferred from a design point of view. Furthermore, image-forming apparatuses of a multiple function type that include functions of a fax and copy machine in addition to a printer are now being widely used.
A system may attempt to add a printer to other functions, for example a fax machine, a copy machine, etc. For example, U.S. Pat. No. 5,095,370 discloses one type of a multiple function type image-forming apparatus. This multiple image-forming apparatus utilizes a turn-around feeding sheet path system, and arranges a scanner in a clearance space of a main body on the basis of a printer. Such an apparatus has realized miniaturization of a an overall size of the apparatus according to a position of the scanner. However, the apparatus disclosed in U.S. Pat. No. 5,095,370 suffers from a drawback in that it cannot establish a straight feeding sheet path in addition to the turn-around feeding sheet path.
The present inventors considered combining such a multiple function image-forming apparatus with the above two feeding sheet path systems. With such a combination, the multiple function image-forming apparatus arranged with the scanner unit on an upper part of the printer, which adopts the above two path systems, could minimize an area of an upper projection of the apparatus. However, the present inventors also identified that with such a combination the turnaround sheet feeding path and the scanning sheet path cross at an upper part of the ejected paper. This crossing of the sheet paths would cause a jam between an image formed sheet and a scanning sheet in the case of the multiple function image-forming apparatus with the scanner arranged on the upper part of the printer. Furthermore, the overall body size of the apparatus would become large if a distance from a bottom point of the ejected sheet stacker in the turn-around sheet path to the cross point is long in order to prevent an image formed sheet and a scanned sheet from jamming at the cross point. Still further, such a multiple function image-forming apparatus would need an input panel in which a user inputs phone numbers of an address in case of a fax, etc.
Therefore, when the multiple function image forming apparatus simply adds a scanner unit on the upper part of a printer unit, the input panel of the apparatus is visible from outside and the appearance is not clear in the case that the apparatus is used as a printer.